System for injecting metered quantity of fuel into engine

ABSTRACT

A system for injecting a metered quantity of fuel into an engine having a fuel injection pump, an electrically controlled metering valve, and a fluid passage connecting the fuel outlet port of the metering valve to the fuel suction port of the fuel injection pump. In the system, the volume of the fluid passage is suitably selected to lie within a specific range so that the metering of fuel by the metering valve is continued for a period of time more than that during which the fuel suction port of the fuel injection pump is kept open.

United States Patent 11 1 Hobo et a1. Oct. 2, 1973 [54] SYSTEM FORINJECTING METERED 3,661,130 3/1970 Eheim 123/139 E QUANTITY OF FUEL INTOENGINE 3,516,395 6/1970 1335501.... 123/139 E 1,664,610 4/1928 French123/32 AE 3,592,177 7/1971 Wehde 123/139 E [75] Inventors: NobuhltoHobo, lnuyama-shi;

Yoshimi Natsume, Toyohashi-shi; Yutaka Suzuki, NishiO-Shi, all OfPrimary Examiner-Laurence M. Goodridge Japan Assistant ExaminerRonald B.Cox

AttorneyCushman, Darby & Cushman [73] Assignee: Nippondenso Co., Ltd.,Kariya-shi, Aichi-Ken, Japan 221 Filed: July 29, 1971 I571 ABSTRACT [2]]Appl' N05 167399 A system for injecting a metered quantity of fuel intoan engine having a fuel injection pump, an electrically 30 Foreign A nfi priority Data controlled metering valve, and a fluid passage connect-Au 10 1970 Ja an 45/69926 ing the fuel outlet port of the metering valveto the fuel p suction port of the fuel injection pump. 1n the system,[52] U 5 Cl 123/32 AE 123/139 E 123/139 Aw the volume of the fluidpassage is suitably selected to 123/139 123/139 lie within a specificrange so that the metering of fuel [5 H hm CL F02) 3/00 Fozm 39/00 bythe metering valve is continued for a period of time [58] Field l23/32EA 32 AE more than that during which the fuel suction port of the"123/139 E 1 fuel injection pump is kept open.

[56] References Cited 2 Claims, 2 Drawing Figures UNITED STATES PATENTS3,568,646 3/1971 Wehde 123/32 EA SYSTEM FOR INJECTING METERED QUANTITYOF FUEL INTO ENGINE BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to fuel injection systems for injectingfuel into engines such as diesel engines, and more particularly to afuel injection system in which an electromagnetically operated meteringmeans and electrical control means for applying a timing pulse to theelectromagnetically operated metering means are used for supplying ametered quantity of fuel to a fuel injection pump in each operatingcycle of the fuel injection pump.

2. Description of the Prior Art A fuel injection pump adapted forintermittent injection of fuel is generally so constructed that the fuelsuction port in the pump cylinder communicates with the pump chamber atthe end of the suction stroke of the pump plunger during the operatingcycle of the fuel injection pump, and in the delivery stroke of the pumpplunger, the pump plunger closes the fuel suction port in the pumpcylinder so as to supply fuel under pressure to the fuel injectionnozzle.

In a system commonly employed for controlling the quantity of deliveryor quantity of fuel injected in each operating cycle of a fuel injectionpump of the kind as above described, an electromagnetically or solenoidoperated valve is interposed in the fluid passage leading to the fuelsuction port of the fuel injection pump from a fuel feed pump supplyingfuel at a low pressure of the order of 2 kilograms per square centimeterand a timing pulse is applied to the solenoid operated valve fromelectrical control means in each fuel suction stroke of the pump plungerof the fuel injection pump so that the solenoid operated valve is openedand maintained in such a position for a period of time determined by theduration of the timing pulse for the metering of fuel. The inventorshave experimentally ascertained the fact that, in such a system, thevolume of the space in the fluid passage ranging from the fuel suctionport of the fuel injection pump to the fuel outlet port of the solenoidoperated valve open and closed by the needle valve member (which spacewill hereinafter be referred to as a stabilizing chamber) is intimatelyrelated with the duration of the timing pulse or period of time duringwhich the metering can be carried out by the solenoid operated valve.More precisely, when the fuel outlet port of the solenoid operated valveis disposed in close proximity to the fuel suction port of the fuelinjection pump and thus the stabilizing chamber has a sufficiently smallvolume, the period of time during which the fuel can be metered by thesolenoid operated valve is limited to the period of time during whichthe fuel suction port is open and communicates with the pump chamber inthe suction stroke of the pump plunger of the fuel injection pump. Onthe other hand, when the fuel outlet port of the solenoid operated valveis suitably spaced from the fuel suction port of the fuel injection pumpand thus the stabilizing chamber of a suitably large volume is providedin the fluid passage therebetween, the fuel can be metered by thesolenoid operated valve not only during the period of time in which thefuel suction port is in its open position in the suction stroke of thepump plunger but also during the delivery stroke of the pump plunger.

Thus, the provision of the stabilizing chamber is especially effectivewhen a single solenoid operated valve is disposed in the:fluid passageleading to the fuel suction port of a fuel injection pump for meteringthe fuel to be distributed to the cylinders of a multi-cylinder dieselengine. Suppose, for example, that a fuel injection pump of thedistributor type fuel injection pump from which fuel is distributed toeach cylinders of a fourcylinder diesel engine is driven from a driveshaft of the distributor type injection pump rotating at a maximum speedof 1,800 r.p.m., then one operating cycle of the fuel injection pumpoccupies a period of time of /1800 X A 0.0083 second. When, in thiscase, the solenoid operated valve is disposed in close proximity to thefuel suction port of the fuel injection pump and a period of time duringwhich the solenoid operated valve is held in its open position is variedto meter a suitable quantity of fuel to be drawn into the pump chamberin each operating cycle of the fuel injection pump, the solenoidoperated valve can only meter the fuel during a limited period of timewhich ranges from the time at the end of the suction stroke of the pumpplunger to the time immediately before the subsequent delivery stroke ofthe pump plunger takes place in the operating cycle of the fuelinjection pump. This period of time is equal, at the most, to the halfof the entire period of time occupied by one operating cycle of the fuelinjection pump. Thus, the metering period of time is of the order of0.004 second at the most when the pump is driven by the shaft rotatingat the maximum speed of 1,800 r.p.m. and it is difficult to attain themetering with high precision.

Further, when the stabilizing chamber has an excessively large volume,the variation in the quantity of fuel delivered from the fuel injectionpump occurs with a certain time lag relative to the variation in thequantity of fuel metered by the solenoid operated valve in eachoperating cycle. The use of such a fuel injection pump with such a poorresponse characteristics for a diesel engine is undesirable in thathunting occurs in the diesel engine.

SUMMARY OF THE INVENTION With a view to overcome the defects describedabove, it is a primary object of the present invention to provide animproved fuel injection system of the electromagnetically metering typecapable of metering fuel with high precision. According to the presentinvention, the stabilizing chamber provided in the fluid passage leadingfrom the fuel outlet port of the solenoid operated valve to the fuelsuction port of the fuel injection pump is selected to have a suitablevolume lying within a predetermined range so that the solenoid operatedvalve can meter the fuel over a period of time which is more than theperiod of time in which the fuel suction port is in its open position inone complete operating cycle of the fuel injection pump. By virtue ofthe above arrangement, the solenoid operated valve can meter the fuelover a period of time which is substantially equal to the period of timeoccupied by one complete operating cycle of the fuel injection pump, andthe metering period of time can be substantially extended to 0.0083second when, for example, the shaft driving the pump is rotating at itsmaximum speed of 1,800 r.p.m.

The above and other objects, features and advantages of the presentinvention will be apparent from the following detailed description of apreferred embodiment thereof taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic frontelevational view partly in section of an embodiment of the presentinvention.

FIG. 2 is a chart illustrating the operation of the fuel injection pumpin the system according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a fuel feedpump 2 draws fuel from a fuel reservoir 1 to supply same to a fuelinjection pump 7 through an electromagnetically or solenoid operatedvalve 4. A pressure regulator 3 is connected between the outlet of thefuel feed pump 2 and the fuel reservoir 1. The solenoid operated valve 4comprises a needle valve member 4a of magnetic material, an energizingcoil or solenoid 4b, a spring 40 normally urging the needle valve member4a against the valve seat, a fuel outlet port 6a and a fuel inlet port6b. An electrical control means generates a timing pulse of a durationcorresponding to the quantity of the fuel required by a diesel engine soas to apply this timing pulse to the solenoid 4b of the solenoidoperated valve 4. The fuel injection pump 7 comprises a pump cylinder11, a pump plunger slidably received in the pump cylinder 11, a fuelsuction port 9 bored in the wall of the pump cylinder 11, and a pumpchamber 12 defined within the pump cylinder 11 by the pump plunger 10. Astabilizing chamber 8 is formed in the fluid passage connecting the fueloutlet port 6a of the solenoid operated valve 4 to the fuel suction port9 of the fuel injection pump 7. A cam follower 14 carried by a rodconnected to the pump plunger 10 engages the cam surface of a cam 13which is rotated in interlocking relation with the drive shaft of thediesel engine. A delivery valve 15 is connected to a fuel injectionnozzle 17 by a high pressure conduit 16.

In operation, the pressure of fuel discharged from the fuel feed pump 2is maintained at a constant value of about 2 kilograms per squarecentimeter by the pressure regulator 3. In response to the applicationof the timing pulse from the electrical control means 5 to the solenoid4b of the solenoid operated valve 4, the needle valve member 4a is urgedaway from the valve seat against the force of the spring 4c so that thesolenoid operated valve 4 is urged to the open position and kept in sucha position for a period of time which is determined depending on theduration of the timing pulse. Thus, during this period of time, ametered quantity of fuel is discharged through the fuel outlet port 6a.The rotation of the cam 13 in interlocking relation with the drive shaftof the diesel engine causes reciprocating movement of the cam follower14, and this reciprocating movement is transmitted to the pump plunger10 which makes reciprocating movement within the pump cylinder 11 tocarry out the pumping action. The fuel outlet port 6a of the solenoidoperated valve 4 communicates now with the fuel suction port 9 of thefuel injection pump 7 through the stabilizing chamber 8. Due to thereciprocating movement of the pump plunger 10 relative to the pumpcylinder 11, the fuel suction port 9 communicates with the pump chamber12 for a period of time which ranges from the time at the end of thesuction stroke of the pump plunger 10 to the time immediately before thesubsequent delivery stroke of the pump plunger 10 takes place in theoperating cycle of the fuel injection pump 7, and the fuel metered bythe solenoid operated valve 4 flows into the pump chamber 12. The numberof operating cycles of the solenoid operated valve 4 is selected to beequal to the number of operating cycles of the fuel injection pump 7 sothat the quantity of fuel supplied to the fuel injection pump 7 in eachoperating cycle is approximately equal to the quantity of fuel passedthrough the fuel outlet port 6a of the solenoid operated valve 4 eachtime it is energized. This fuel is forced through the delivery valve 15and the high pressure conduit 16 to be injected by the fuel injectionnozzle 17 during the delivery stroke of the pump plunger 10.

If the fuel outlet port 6a of the solenoid operated valve 4 is disposedin close proximity to the fuel suction port 9 of the fuel injection pump7 and thus the fluid passage connecting therebetween has a sufficientlysmall volume, the period of time during which the fuel is supplied intothe pump chamber 12 of the fuel injection pump 7 due to the openposition of the solenoid operated valve 4 is naturally limited to theperiod of time during which the fuel suction port 9 communicates withthe pump chamber 12. However, due to the fact that the stabilizingchamber 8 is provided in the fluid passage leading from the fuel outletport 6a of the solenoid operated valve 4 to the fuel suction port 9 ofthe fuel injection pump 7 and the total volume of the fluid passageincluding the stabilizing volume chamber 8 is selected to be larger thana predetermined value as seen in FIG. 1, a space is produced in aportion of the stabilizing chamber 8 for receiving therein the quantityof fuel to be metered by the subsequent operation of the solenoidoperated valve 4. Thus, this quantity of fuel metered by the solenoidoperated valve 4 can pass through the fuel outlet port 6a into thisspace irrespective of whether or not the fuel suction port 9 of the fuelinjection pump 7 communicates with the pump chamber 12. This quantity offuel is delivered to the fuel injection nozzle 17 in the subsequentdelivery stroke of the pump plunger 10 of the fuel injection pump 7.

The stabilizing volume chamber 8 may have a largest possible volume asfar as the supply of the fuel metered by the solenoid operated valve 4into the fuel injection pump 7 is concerned, but there is a minimumstabilizing which is determined by various factors including the periodof time in which the solenoid operated valve 4 is kept open, the maximumdischarge capacity of the fuel injection pump 7, the period of time inwhich the solenoid operated valve 4 is in its open position and the fuelsuction port 9 of the fuel injection pump 7 communicates with the pumpchamber 12, and the quantity of fuel metered by the solenoid operatedvalve 4.

FIG. 2 shows the results of measurement on the fuel injection pump 7which is adapted for distributing fuel to four cylinders ofa dieselengine and in which the volume of the pump chamber varies by Vb mm ineach operating cycle for supplying fuel to one cylinder. In FIG. 2, thehorizontal axis represents the number of revolutions N per minute of theshaft driving the pump, the vertical axis represents the quantity ofdelivery Q mm lstcy per cylinder in each operating cycle, and the periodof time T during which fuel is metered by the solenoid operated valve 4is taken as a parameter. The solid lines in FIG. 2 represent theoperating characteristics when the stabilizing chamber 8 has a volume Va150 mm, while the broken lines represent similar characteristics whenthe fuel outlet port 6a of the solenoid operated valve 4 is disposed inclose proximity to the fuel suction port 9 of the fuel injection pump 7so that the stabilizing chamber 8 has an extremely small volume Va mm.It will be apparent from FIG. 2 that, when the volume Va of thestabilizing chamber 8 is Va 150 mm and the metering period of time T ofthe solenoid operated valve 4 lies within the range of T 7 msec, thequantity of delivery Q is independent of the number of revolutions N ofthe drive shaft of the fuel injection pump and is determined primarilyby the duration of the timing pulse applied to the solenoid 4b of thesolenoid operated valve 4, and the metering can be reliably attained upto the number of revolutions N 1,800 rpm. However, with the volume Va 20mm of the stabilizing chamber 8, the quantity of delivery Q is abruptlydecreased with the increase in the number of revolutions N beyond N1,000 r.p.m. in the case of the metering period of time T 7 msec andthus reliable metering of fuel cannot be attained.

Therefore, as far as the metering of fuel is concerned, the volume Va ofthe stabilizing chamber 8 should be so selected as to satisfy therelation Va 2 e Vb where e is a constant which lies in the range of 0.1to l and Vb is the variation in the volume of the pump chamber 12 of thefuel injection pump 7 in each operating cycle. The metering of fuel bythe solenoid operated valve 4 can be reliably carried out when Va isselected to satisfy the above relation. However, the provision of thestabilizing chamber 8 adversely affects the transient response of thefuel injection pump 7 and this transient response becomes worse with theincrease in the volume Va of the stabilizing chamber 8.

The lag of the variation in the quantity of fuel delivered from the fuelinjection pump 7 relative to the variation in the quantity of fuelmetered by the solenoid operated valve 4 may be considered as a firstorder lag. The rate of variation v in the volume per second is given byv N/60'M-Vb where Vb is the variation in the volume of the pump chamber12 in one operating cycle of the fuel injection pump 7, N is the numberof revolutions per minute of the shaft driving the pump, and M is thenumber of operating cycles of the fuel injection pump 7 during onerotation of the drive shaft. in this case, the time constant Td of thefirst order lag is given by Td Va/v 60/N-Va/MVb.

Hunting in the rotational speed of the diesel engine equipped with thefuel injection pump 7 having such operating characteristics is closelyassociated with factors such as the coefficient of inertia of the engineand the operating conditions of the engine, but no problem of huntingarises when the volume Va of the'stabilizing chamber 8 has anexperimentally determined approximate value satisfying the relation Va 51 MVb where 17 is a constant which lies in the range of l to 5.

From the above discussion, the practically preferred value of the volumeVa of the stabilizing chamber 8 should lie in the following range:

0.1 Vb Va 5 MVb When the volume Va of the stabilizing chamber 8 isselected to be a suitable value lying within the range satisfying therelation (1) above described, the fuel can be metered by the solenoidoperated valve 4 even when the fuel suction port 9 of the fuel injectionpump 7 is closed by the reciprocating pump plunger 10 and thus themetering period of time of the solenoid operated valve 4 can be extendedto a value which is substantially equal to the total period of timeoccupied by one operating cycle of the fuel injection pump 7. Further,the diesel engine equipped with this fuel injection pump 7 is quite freefrom undesirable hunting.

It will be understood from the foregoing description that, in the systemaccording to the present invention, the volume Va of the fluid passageleading from the fuel outlet port of the solenoid operated valve openand closed by the needle valve member to the fuel suction port of thefuel injection pump is selected to lie within the range satisfying therelation 0.1 Vb 2 Va 5 MVB, where Vb is the variation the volume of thepump chamber during one operating cycle of the fuel injection pump and Mis the numberof operating cycles of the fuel injection pump during onerotation of the drive shaft of the diesel engine. By virtue of the abovearrangement, the solenoid operated valve can meter the fuel for a periodof time which is more than that during which the fuel suction port ofthe fuel injection pump is kept open due to the suction stroke of thepump plunger. That is to say, the solenoid operated valve can meter thefuel even in the period in which the fuel suction port of the fuelinjection pump is closed due to the delivery stroke of the pump plunger,and thus the metering period of time can be substantially extended tothe period of time occupied by one complete operating cycle of the fuelinjection pump. The present invention is therefore advantageous in thatfuel can be metered with high precision and no hunting occurs in thediesel engine equipped with the fuel injection pump.

We claim:

1. A system for injecting a metered quantity of fuel into an enginehaving a crankshaft comprising:

a cam shaft rotated at a constant speed reduction ratio by said enginecrankshaft,

a fuel injection pump, including a cylinder, a piston reciprocated insaid cylinder to deliver fuel and defining within said cylinder a pumpchamber, said cylinder having a fuel suction port for receiving fuelwhich is opened by said piston during a fuel receiving cycle portion andclosed by said piston during a fuel delivery cycle portion,

electromagnctically operated metering means having a fuel inlet port anda fuel outlet port,

electrical control means connected to said electromagnetically operatedmetering means for applying a timing signal having a time durationdetermining the amount of fuel injected during a cycle to said meteringmeans to operate said metering means during said cycle portions, and

means defining a fluid passage connecting the fuel outlet port of saidelectromagnctically operated metering means to said fuel suction port ofsaid fuel injection pump for receiving via said metering means duringeach said cycle a quantity of fuel as determined by said timing signalso that the fuel in said fluid passage passes via said fuel suction portinto said pump chamber during each said fuel receiving cycle portion,

wherein the volume Va of said fluid passage is so selected as to liewithin the range satisfying the relation 0.1 Vb Va MVb, where Vb is thevariation in the volume of the pump chamber during one operating cycleof said fuel injection pump and M is the number of operating cycles ofsaid fuel injection pump during one rotation of the drive shaft, 5

whereby the metering of fuel by said electromagnetically operatedmetering means is continued for a period of time which is more than thatduring closing the fuel outlet port.

1. A system for injecting a metered quantity of fuel into an enginehaving a crankshaft comprising: a cam shaft rotated at a constant speedreduction ratio by said engine crankshaft, a fuel injection pump,including a cylinder, a piston reciprocated in said cylinder to deliverfuel and defining within said cylinder a pump chamber, said cylinderhaving a fuel suction port for receiving fuel which is opened by saidpiston during a fuel receiving cycle portion and closed by said pistonduring a fuel delivery cycle portion, electromagnetically operatedmetering means having a fuel inlet port and a fuel outlet port,electrical control means connected to said electromagnetically operatedmetering means for applying a timing signal having a time durationdetermining the amount of fuel injected during a cycle to said meteringmeans to operate said metering means during said cycle portions, andmeans defining a fluid passage connecting the fuel outlet port of saidelectromagnetically operated metering means to said fuel suction port ofsaid fuel injection pump for receiving via said metering means duringeach said cycle a quantity of fuel as determined by said timing signalso that the fuel in said fluid passage passes via said fuel suction portinto said pump chamber during each said fuel receiving cycle portion,wherein the volume Va of said fluid passage is so selected as to liewithin the range satisfying the relation 0.1 Vb < OR = Va < OR = 5 MVb,where Vb is the variation in the volume of the pump chamber during oneoperating cycle of said fuel injection pump and M is the number ofoperating cycles of said fuel injection pump during one rotation of thedrive shaft, whereby the metering of fuel by said electromagneticallyoperated metering means is continued for a period of time which is morethan that during which the fuel suction port of said fuel injection pumpis kept open.
 2. A system as claimed in claim 1, in which saidelectromagnetically operated metering means is a solenoid operated valvehaving a needle valve member normally closing the fuel outlet port.